I am currently replacing a wall oven and cooktop with a slide in range. Both have there own 240v 30 amp circuit breakers and comes into a junction box under the cooktop. The new slide in requires a 40 amp circuit. Can I use the existing #10 wires if I double and tie them together? In theory this would make them equivalant to a 5 gauge. The 40 amp breaker would then have 2 #10 gauge wires connected to each terminal. The 2 -30 amp breakers would be taken out and replaced with the 40 amp. I know that the proper way is to run a new #6-50 or #8 -40 wire but the above method is easier to do.